I installed XAMPP on my local machine (desktop computer) which is running Windows XP and discovered that I was not able to start the Apache server service until I stopped the Windows Internet Information Service (IIS) that was running on my machine.

This probably will not apply to everyone running Windows, because I don't think that IIS runs by default, but it could be a very annoying snag for some users. I seem to recall that I enabled IIS when I did some ASP development.... I didn't see this complication mentioned in the XAMPP documentation or Help system....

In Windows XP
To stop the IIS service, go to Start/Control Panel/Administrative Tools and double-click on Internet Information Services. Then in the left panel, expand the local computer node and the Web Sites node. Right click the Default Web Site and select Stop from the shortcut menu.
Another option, if you are not going to use IIS, is to remove it from your Windows installation. This can be done by clicking Start/Add Or Remove Programs and selecting Add/Remove Windows Components, and then unchecking the box next to Internet Information Services (IIS).

I hope this helps somebody....